Someday, not too far in the future, local areas throughout the Bay watershed may be assigned “budgets” for nitrogen and phosphorus.

Every time a wastewater treatment plant is expanded, a new housing development is approved or an animal feedlot is established, their nutrient increases would have to be offset so that the overall budget stays in balance.

Those offsets could be achieved by such means as improving stormwater management at an older development, using new technologies to better treat wastewater plant effluent or employing new runoff control techniques on farm fields.

That, at least, is the future broadly painted by new reports from Maryland and Virginia that discuss how to maintain nutrient “caps” in the watershed.

Both talk about difficulties in achieving a “no net increase” in nutrients in the face of population growth. Both call for “lifestyle changes” in which people opt to live in more compact developments, are urged to drive less — and even do a better job of scooping up dog droppings.

Virginia even suggests a mass-media advertising campaign to drive the point — literally — home.

The strategies stem from a 1992 commitment by the Chesapeake Executive Council — the governors of Maryland, Pennsylvania and Virginia; the District of Columbia mayor; the EPA administrator; and the chairman of the Chesapeake Bay Commission, which represents state legislatures — to achieve nutrient reductions assigned for major tributaries and then “maintain that reduced load thereafter.”

That reduced level has since become known as a nutrient “cap.”

In late March, Maryland produced a strategy showing how it would hold the line on nutrients, while Virginia released a draft strategy for its portion of the Potomac and Shenandoah basins for public comment. (Other Virginia tributaries were only recently assigned nutrient loads and did not need cap strategies.)

In reality, neither state has yet achieved the year 2000 reduction goals they are to maintain. According to Bay Program figures, Virginia’s Potomac-Shenandoah basin was about 3.7 million pounds short for nitrogen, but achieved its phosphorus goal. Maryland was about 2.4 million pounds short for nitrogen, but achieved its phosphorus goal.

Both the Maryland and Virginia strategies envision closing that gap within the next couple of years, largely as wastewater treatment plants are upgraded with nutrient control technology.

Pennsylvania, which was 8 million pounds short for nitrogen, and 140,000 pounds short for phosphorus, is not expecting to complete a cap strategy until late spring or early summer.

The Maryland and Virginia strategies both suggest that continued implementation of current activities will come close to holding the line on nutrients, but some new actions will be needed.

And, officials in both Maryland and Virginia acknowledge that their documents are not comprehensive, long-term strategies to hold the line on nutrients.

Rather, both states view their cap strategies as transitional documents that will prompt people to think about how they will achieve the further nutrient reductions needed to meet the Bay Program’s 2010 cleanup goal — a figure to be developed later this year — and then maintain that nutrient cap.

The cap concept means a fundamental change in the way nutrients are dealt with. Instead of having a one-time nutrient reduction goal, it requires continued efforts to find ways to offset nutrient increases until sometime — if ever — the watershed’s population stops growing.

The strategies, officials say, are a starting point for public discussion about how that will happen.

“We wanted to present this as part of an ongoing process, so it wouldn’t seem like we were coming back to the watershed every two years with another plan that we wanted them to do,” said Gary Waugh, of the Virginia Department of Conservation and Recreation, who helped to develop the draft strategy. “This is part of an ongoing process, and an ongoing commitment to improving water quality.”

Continued nutrient reductions are a challenge because more people result in more nutrients. Nitrogen oxides are produced from fossil fuel combustion from power plants and automobiles. Excess fertilizer placed on fields, lawns and golf courses results in nitrogen that flows into local streams or sinks into groundwater. Wastes from humans and animals — including household cats and dogs — are laden with still more nutrients.

As a result, scientists have estimated that six to eight times as many nutrients enter the Bay today as they did during pre-settlement times.

Those nutrients cause excessive algae blooms, which block sunlight from reaching beds of underwater grasses that provide habitat for juvenile blue crabs, fish and waterfowl. When the algae die, they sink to the bottom and decompose in a process that creates an oxygen-depleted “dead zone” lethal to most aquatic life.

The problem is not limited to the Bay. A National Academy of Sciences report last year estimated that, globally, human activities have increased the amount of nitrogen available in the environment two– to-threefold since the 1950s.

Excess nutrients are already considered the greatest threat to coastal waters, and the problem is expected to grow as more land is converted to support and feed the planet’s growing population.

Continuing to run counter to that global trend will be difficult, both state strategies acknowledge. Many of the reductions achieved so far came from the easiest, cheapest sources to control. As a result, achieving and maintaining future reductions will likely mean addressing smaller sources of pollution, and at a greater expense.

Ultimately, both reports agree that programs must be developed to eliminate nutrient pollution from any new source, or find ways to offset that increase. Neither strategy provides details about how that will happen.

“I wish it could have had more final answers, but the reality was it identified a lot of issues for which we must develop final answers,” said Tom Simpson, a professor in the University of Maryland’s College of Agriculture and Natural Resources, and co-chair of the group that wrote the Maryland strategy. “And that is a real value.”

Indeed, both strategies present a laundry list of big issues that must be dealt with in the future.

Past reductions were achieved over a broad scale — Maryland divided reductions among 10 large watersheds, while Virginia sought reductions throughout the Potomac-Shenandoah basin. In the future, as nutrient increases and decreases must be more carefully tracked, both strategies envision more localized nutrient allocations.

Mainly, that’s because most of the activities to control nutrients hinge on local action. That would include better stormwater management, having site designs for new development that would reduce runoff, and upgrades at wastewater treatment plants.

Neither strategy recommends a specific scale for managing nutrient loads, although both suggest counties may be the appropriate level. But both states said better models have to be developed before loads can be assigned at such local levels.

The Bay Program uses a computer model of the Bay watershed to determine the amount of nutrients entering the Chesapeake from each tributary. While it provides large-scale estimates of nutrient loads, it is not considered accurate enough to assign loads at a smaller scale.

The strategies also agree that there needs to be a better accounting of all nutrient increases and decreases. While formulas exist to credit nutrient benefits for a variety of agricultural practices, the benefits of activities ranging from wetland creation and stream restoration to street sweeping and better growth planning are more difficult to credit.

In addition to measuring benefits from uncounted actions, the strategies suggest a harder look at existing nutrient controls to make sure they are delivering promised reductions.

The Maryland strategy notes that the effectiveness of some nutrient control practices — such as stormwater systems and agricultural buffers — may deteriorate over time unless they are maintained.

Monitoring nutrients additions and decreases — and accounting for offsets — will be extremely complex. A new wastewater treatment plant that replaces aging septic systems could result in nutrient reductions. On the other hand, a plant being built to accommodate new growth would probably add nutrients, and require offsets.

And someone has to track all of that. The Virginia strategy suggests that “lines of responsibility” must be established and backed with sufficient authority to ensure nutrient offsets are achieved and accomplished. Such authority, it said, may be established through local ordinances, inter-local agreement, state permits or another legal contract.

Waugh stressed that the strategy was not making firm recommendations about how programs should be shaped, but providing “major concepts that we need to look at.” He said the state would like to start a dialogue on those issues during the comment period.

But, he added, some issues will be difficult and controversial. “Whenever you start actually looking at lines of responsibility, there is going to be some confrontation,” Waugh said. “That is why we want this to be a process where we get as many people involved as possible.”

Another major challenge, cited in the Virginia strategy, will be finding ways to allow growth in areas that want to attract development, without violating the cap. “The strategy is not intended to cap growth in the basin, but is designed to cap the nutrient load impacts associated with that growth,” the Virginia document states.

To deal with such issues, both strategies suggest that nutrient trading programs may be needed in the future. The Bay Program recommended a potential framework for such trading programs in the region.

The strategies acknowledge that states will be big players, largely because of the need for stepped-up funding for grant and cost-share programs that support nutrient reduction efforts. Neither strategy offers a cost estimate, but both suggest the tally will be large.

Simpson said when the Maryland strategy findings were presented to department heads and other officials who make up the governor’s “Bay Cabinet,” the presentation concluded by saying future actions will require “big new ideas, big new policies and big new finances.

“It was one of the more direct, hard-hitting presentations of upper level bureaucrats to appointees that you will ever see.”

The task ahead is big enough, according to the Virginia strategy, that during meetings leading up to the draft strategy, some stakeholder groups said they were willing to forgo cost-share money to support a massive outreach campaign to educate suburban and urban homeowners about how their cumulative actions regarding such things as septic system treatment, lawn care, pet droppings and driving degrade water quality.

The strategy suggests a multistate advertising campaign to raise awareness about how individuals affect the Bay. “If you are going to ask people to change their lifestyles and change their behavior, you are going to need to explain to them why, and make them aware of the benefits,” Waugh said. “And that is why we placed such an emphasis on the public education component.”

There is, after all, no end in sight for nutrient controls. The Virginia strategy flatly states that the job of controlling nutrients in the Potomac-Shenandoah basin — which experienced a 23 percent population growth from 1990–2000 — will be finished only when the basin “is no longer experiencing population growth or new land conversion.”

The Maryland strategy and supporting technical documents are available online at www.dnr.state.md/bay/tribstrat/index.html

The Virginia strategy is available at www.dcr.state.va.us, or www.deq.state.va.us, or by calling 1-877-42WATER. The state is accepting comments on the draft strategy through June 1.